Process of purifying chemicals



Patented Jul so, 1929.

umrao STAT-ES wan'rnn warm, or nussnnnoar,

success or roan-me cannons ueonr, or .anuna'rn-ou-ran-namn,

Io Drawing. Application med September 7, 1827, Serialll'o. 218,118, am! in Germany December 24,19.-

Our invention relates to a process of purifying chemicals intended for use as the raw materials in the manufacture of roducts containg active oxygen. It 1s wel under- 6- stood that chemica s which are to be used 4 for the manufacture of products containing active en, must, be very pure. Even very smzfi quantities of impurities which are liable to exercise a decomposing effect by 10 catalytic action on the so called per compounds, reduce the yield to a large extent and moreover afl'ect the durabillty of the product obtained. In theinterest of economy in this branch of industry 1t is'of paramount importance to avoid as far as possible the presence of any impuritles having a catalytic 'acpion. For example, in the, -manufacture o perborates and percarbonates, the degree of purity of the raw Inaterials, such as borax,caust1c soda and calclned soda, cannot be too great. This applles more particularly to electrolytic processes of manufacture. Also in the manufacture of hydrogen peroxide, persulphates and perphosphates, the chemicals WhlCll act as oxygen carriers, must be submitted to a very thorough purification in order to free them from catalyzers. This condition is generally dealt wlth by recrystallization. It has been found .however that the yield of oxygen and the durability of the product are unfavourably affected by the presence in thestarting material of catalytically acting substances in such minute quantities that they can not be practically ascertained for anal sis. For example'the small quantities o heavy metals. which are normally contained in water from.

the tap and even in distilled water, are of 40 considerable influence.

be chiefly manganese, copper and exceedingly small traces of platinum. I

As a result of prolonged experiment we have found that these small quantities of 4 catalyzers can be eliminated by treating the solutions of the raw materials to be purified, in a suitable/manner with silica gel which appears to have the property of absorbing the disturbing catalayzers without limit.

For example, a borax or soda solution, from which such quantities of heavy metal compounds as can be precipitated have preferably been previously separated, may, before Such metals seem to it is crystallized, be boiled, while being stirred, with silica gel in the form of a powder. We have found that'2 kg. silica el are suflicient for 1 cbc. m. of solution. he salts crsytallized out of the clear decanted solution, when converted into the corre spondmg percompoundn givethe highest y1elds and products of excellent durability. The solutions of chemicals can also be stirred, while cold, with silica l but the latter treatment takes a somew at longer time. However, the latter treatment may be employed, for example, when it is not deslre to se arate the chemicals in a state from t eir solutions, and where the solutions themselves are to be used as, for 1nstance, when preparing sodium perborate by the addition of hydrogen peroxide to a solution of sodium meta-borate. Y

As is known, silica gel is a glass-like, more or less fine-grained mass of pure silicic acid, which has a eat internal surface development. (See or instance Meyer, Zeitschrift fiir angew. Ghemie, vol. 37, 1924, p. 36 and 209 andU. S. Patent No. 1297 24.) The silica gel, after use, can be regenerated by washing, treatment with acid and subsequent heating, in the known manner. It should be remarked that the invention 1s susceptible of modifications and changes to conform to varying conditions of a plication within the scope of the claims ereunto appended.

We claim z? 1 1. A rocess of removing catalytic substances rom chemicals intended for use as the raw materials in the manufacture of PATENT o F Icaproducts containing active oxygen,'consisting in adding silica gel to the chemicals in solution and separating the solutions from silica gel. t

2. A process of removing catalytic substances from chemicals intended for use as the raw materials in the manufacture of products. containing active oyxgen, consist-- rocess of removing catalytic subsolution, heating and stirring the mixture solution, heating and stirring the mixture and separating the solution from silica gel. separating the solution from silica gel an 4. A rocess of removing catalytic suballowing the solution to crystallize.. 10'

stances rom chemicals intended for use as In testimony whereof we have hereunto 5 the raw materials in. the manufacture of set our hands.

products containing active oxygen, consist- WALTER WEBER. ing in adding silica gel to the chemicals in MAX JAOOBL 

